A. Field of the Invention:
The present invention relates to fluid flow meters and more specifically to a method and apparatus for measuring of fluid flow including liquids, gases, and vapors, in extreme temperature ranges varying from cryogenic to greater than 1000.degree. F.
B. Description of Prior Art
The general principles of electronics and instrumentation theory are widely known and have been applied for many years to perform real-time measurements of fluid flow, such as liquids, gases, or vapors flowing in pipelines. However, the adverse effects of temperature extremes in the flowing fluids, as well as vibrations, noise, and shocks in the flow pipes, have either prevented or impeded adequate flow measurement, and, in some circumstances, the limits of instrumentation have detracted from the effectiveness and efficiencies of plant operations.
By way of example, steam generation is a historic and widespread process used to power much of industry's machinery as well as to heat regional and commercial and industrial buildings. The ability of steam to perform work is in part determined by its temperature. Monitoring of the flow (as well as other parameters) of steam is necessary in industrial applications, from the standpoint of proper plant function, process control, efficiency, and billing. However, operations to which monitoring is critical may be limited by the temperature ranges over which the monitoring devices themselves may function. Further, operations in which avoidance of shutdown or interruption is critical may find insertion-type monitoring devices to be more suitable to their needs than full-bore meters.
In attempts to meet needs such as these, a wide variety of meters utilizing a variety of electronic instrumentation techniques have been developed and are well known in the industry. For example, turbine meters utilizing rotors and magnetic coil pickups, sonic sensors utilizing doppler frequency shifts, vortex-generating sensors, and electromagnetic sensors have widespread applications. All of these instruments and techniques, however, are limited by the degree of temperature that the electronic components associated directly with their sensors or pickup apparatus are able to withstand. The practical upper temperature limit of these devices, above which such conventional electronic instrument components in prior art devices fail, has been in the range of 750.degree.-800.degree. F. A measuring device that can be inserted into, and extracted from, a flow pipe and maintainable without line shutdown and which could significantly extend the upper operating temperatures limits within the pipe from the present practical limits of 750.degree.-800.degree. F. to above 1000.degree. F. would significantly increase the efficiency and management capabilities of a steam system. Such a flow measuring device would be even more beneficial if it was applicable to systems employing flows of dirty or corrosive fluids as well as clean liquids, gases, or steam. Such a flow meter device that could even function at cryogenic temperatures would significantly improve the state of the art even further.